'Frames' are the smallest datablocks handled by the Backend. The application tells the Backend to make [[File]]s availabe and then only requests Frames from the Backend, all other datastructures of the backend are private. -Actually Frames are blocks of continous memory, they can be anything depending on the usage of the [[File]] (Video frames, encoder frames, blocks of sound samples). +Actually Frames are (references to) blocks of continous memory, they can be anything depending on the usage of the [[File]] (Video frames, encoder frames, blocks of sound samples). + +Each [[Frame]] points to a [[FrameDescriptor]] which describes the shared properties of [[Frame]]s of the same kind. For video frames this [[FrameDescriptor]] will define the policies of the used color modell, resolution, aspect ratio and so on, for example. Frames are referenced by a smart-pointer like object which manages the lifetime and caching behaviour. There are 3 states such a frame reference can be: # readonly: the backing FileMap is checked out from the aging list, frames can be read